Intake, and vaccum question

[budDynabuick]

Hello all!!! If a leaking (not properly sealed) intake man is allowing just enough

oil into the cyl to foul the plugs, would this show on a vac gauge? If so, what would it look like? Thanks.

Keith

[Roadhog]

Any vacuum leak will show opn a vacuum gauge, I doubt that this is your problem though. Check vacuum and if it is ok then do a comp. test, if it checks out then you probably have valve stem/seal problems.

[NTX5467]

I think that about the only way that you'd get an intake manifold that was sucking oil past the intake gasket would be if the cylinder heads had been milled a bunch or "angle milled" (which would be SERIOUS drag race engine stuff for a V-type engine). In either case, the intake manifold that was used with that pair of heads would also need to be milled/surfaced to match. OR intake manifold bolts that were loose, which could cause a vacuum "seep" anyway. As long as everything is basically "unmolested" stock, I concur with the valve stem/seal orientation.

Enjoy!

NTX5467

[Smartin]

Also, if there was a vacuum leak, it would create a lean condition....not rich.

[Guest Albert]

are you fouling just one plug? I had an engine that was burning oil badly and a friend asked me if i could change it for him, so i did. afterwards i pulled the plugs and found only one was foiled up so i pulled that side to see why.. I found Pink oil on the top of the piston..Then i knew every thing, nothing wrong with the motor at all. the vacuum modulatod went and the motor was sucking trannin fluid into the intake.. last year a friend in town here had his tranni serviced because he kept loosing oil in it, again no major leaks could be seen on the bottom, about a month later the gear shift cable broke so he asked me to change the cable, and said somthing about the missing tranni fluid, so i pulled the vacuum line off the modulator, and pink fluid came out of the line, so he picked up a new modulater, and has not put tranni fluid in it in over a year..

[Jolly_John]

Forgive my ignorance (and forget about the sucking trans fluid situation)....but where would the engine oil come from that a poorly sealed intake manifold could be passing into the cylinders? In other words, no oil customarily passes through the intake manifold, so what would be the source of the oil? Thanks, John

[Clipper47]

Oil can be sucked into the intake ports from the valve lifter gallery beneath the intake manifold if the gasket is leaking.

[budDynabuick]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I think that about the only way that you'd get an intake manifold that was sucking oil past the intake gasket would be if the cylinder heads had been milled a bunch or "angle milled" (which would be SERIOUS drag race engine stuff for a V-type engine). In either case, the intake manifold that was used with that pair of heads would also need to be milled/surfaced to match. OR intake manifold bolts that were loose, which could cause a vacuum "seep" anyway. As long as everything is basically "unmolested" stock, I concur with the valve stem/seal orientation.

Enjoy!

NTX5467 </div></div>

[budDynabuick]

Hey, and thanks for the help! I will try and keep this co-herentLOL.

Quote-Any vacuum leak will show opn a vacuum gauge, I doubt that this is your problem though. Check vacuum and if it is ok then do a comp. test, if it checks out then you probably have valve stem/seal problems.

This is a 63 special 2152v and is pulling 19 in vac. comp 135+-10 oil 35 at 2400rpm 20 at hot idle. Wouldn't valve stem/seals show up on a vac gaugen also?

Quote-I think that about the only way that you'd get an intake manifold that was sucking oil past the intake gasket would be if the cylinder heads had been milled a bunch or "angle milled" (which would be SERIOUS drag race engine stuff for a V-type engine).

I have also heard that sometimes the end seals can slightly raise the intake causing a poor seal. My son installed this intake (with the end seals) while I was away and since he's always in a hurry i am not confident it was properly installed.

Quote-Also, if there was a vacuum leak, it would create a lean condition....not rich.

I have heard it said that there is one condition where-in a vac leak could cause a rich condition. a vac leak could cause (I think)the power piston in the carb to malfunction causing a "rich" condition. Don't know if true, just what i heard.

quote-are you fouling just one plug? I had an engine that was burning oil badly and a friend asked me if i could change it for him, so i did. afterwards i pulled the plugs and found only one was foiled up so i pulled that side to see why.. I found Pink oil on the top of the piston..

All of the plugs are fouling and since this is a dynaflow, trans fluid is not an issue.

quote-Oil can be sucked into the intake ports from the valve lifter gallery beneath the intake manifold if the gasket is leaking.

This being the case, my theory is that since oil is fluid that a "little" (just enough to foul the plugs at idle) could be seeping into the combustion chamber without being obvious on a vac gauge? Btw, ign is in good order. Since the carb (two of them) was rebuilt by my son (the one always in a hurry) it is suspect! I have a very good spare engine i could drop in but I would like to figure this problem out. Ideas/theories appreciated. Thanks.

Keith

[Only Buicks]

Kevin,

If you figure this out you need to let me know what you found. You can see my post just below yours. I have been running in compete circles (now on two engines) just trying to solve a problem with blue smoke puffing out my exhaust pipe. This is on a straight 8, I have 4 (center) wet plugs and 4 (outboard) dry plugs. I suspect something going on with either the intake, carb or valves but can not figure out which needs attention.

Good luck with yours!

[NTX5467]

With the additional information, I believe that you need to determine if the fouled plugs are being fouled from fuel or from oil. On the plug, the two sources mentioned look totally different in what they leave behind.

Fuel fouled will be black and fluffy and oil fouled will be oily. I suspect that when you detemine that, it can possibly reveal where you need to be looking.

A vacuum leak can result in a richer mixture, if the leak is large enough to cause lower intake manifold vacuum (below 10" Hg, maybe more close to 6" Hg vacuum) that will cause the power valve to open and supply richer than normal mixture to the cylinders (possibly to compensate somewhat for the added air from the vacuum leak?).

Just some thoughts,

NTX5467

[Smartin]

That would have to be a huge vacuum leak.

[budDynabuick]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Kevin,

If you figure this out you need to let me know what you found. You can see my post just below yours. I have been running in compete circles (now on two engines) just trying to solve a problem with blue smoke puffing out my exhaust pipe. This is on a straight 8, I have 4 (center) wet plugs and 4 (outboard) dry plugs. I suspect something going on with either the intake, carb or valves but can not figure out which needs attention.

Good luck with yours! </div></div>

Hey Glenn. I will certainly let you know what comes of this.

Keith

[budDynabuick]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Oil can be sucked into the intake ports from the valve lifter gallery beneath the intake manifold if the gasket is leaking. </div></div>

hello all. Since I got more questions than anwsers/thoughts for my initial question lol let me pose/re-phrase it. this is hard for me to put in print so bear with me please. My thoughts are if oil (just a little) is being sucked into the cyl and since oil is liquid, wcould/could it not seal the leak thereby preventig it from showing as a vac leak on a gauge? Any thoughts/oppions to this question are appreciated. Thanks

Keith

[Clipper47]

I think that to a degree an oil leak would seal while it is being sucked past the gasket at least to a certain degree that might not show on a vacuum gauge. I am not familiar with you engine but I once had a 350SB Chev with a leak on the underside of the intake. I drove about 400 miles all highway and it ran fine but it burned as I recall about 3-4 quarts of oil. I took the manifold of and replaced the gaskets, torqued it to spec and it ran fine again without the oil burning. My only conclusion was that the gasket was leaking and sucking oil up through the lifter gallery beneath the manifold.

[Smartin]

Keith, have you looked into other things like properly working ignition components? A poorly firing ignition system will foul plugs fast. Is the carburetor setup properly? Has it been rebuilt?

Are you consuming oil at a fast rate? If so, I would suspect bad rings before any vacuum leaks sucking oil. The only place oil could get to the combustion chambers, is if the head gasket was leaking, or the rings are worn, or as previously stated - the valve seals are bad. Valve seal problems are typically only a problem at startup, where you will see a puff of smoke when the oil burns off inside the combustion chamber. Drivability should not be effected, unless the seals are reallllllly bad.

[budDynabuick]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Keith, have you looked into other things like properly working ignition components? A poorly firing ignition system will foul plugs fast. Is the carburetor setup properly? Has it been rebuilt?

Are you consuming oil at a fast rate? If so, I would suspect bad rings before any vacuum leaks sucking oil. The only place oil could get to the combustion chambers, is if the head gasket was leaking, or the rings are worn, or as previously stated - the valve seals are bad. Valve seal problems are typically only a problem at startup, where you will see a puff of smoke when the oil burns off inside the combustion chamber. Drivability should not be effected, unless the seals are reallllllly bad. </div></div>

Hey Adam. As I already stated i checked "everything", comp, vac, oil pressure as well as the ign are in top working order. Once again,the reason the intake is suspect is my son installed it and he is always in a "big" hurry and I don't trust (I will pull intake soon to check)his work. I'm not saying it "is" the intake (I'm leaning toward the carb) causing my prob. I just thought this was a good question (as well as possilby being my problem) to get an anwser for particularly since i have never the question asked. As Dave K stated, I also think that oil being liquid would tend to seal the intake thereby not showing as a vac leak on a gauge.I also have never heard this question discussed anywhere so I thought it was a good one.

Adam quote-The only place oil could get to the combustion chambers, is if the head gasket was leaking, or the rings are worn, or as previously stated - the valve seals are bad. Valve seal problems are typically only a problem at startup,

This is not a completely accurrate statement as oil

"can" enter the combustion chamber (as was already stated) from under the intake. Also. I get no smoke on startup or any other time for that matter.also, if it were a head gasket, rings,guides, as you say, these would definitly show on a vac gauge so I have ruled these out completely, but thanks for the suggestion. If anyony has any mor insight on my question, it would be appreciated. Thanks Dave for responding to my question. Later

Ps- Dave did you take a vac reading when you had your problem?

Keith

[NTX5467]

When you check compression, you are ONLY checking the seal of the upper "compression rings" of the total piston ring set--period. The upper rings can seal compression well, BUT the OIL CONTROL RING package is what actually scrapes the oil from the cylinder walls and if they are weak or worn, will not do a very good job of what they are supposed to be doing. Similar if they might happen to be "stuck" or otherwise.

If the engine has a good bit of miles on it, the efficiency of the oil rings can be more questionable than you might suspect--especially on an engine built/designed many decades ago.

We can discuss this issue at length for many moons (even MOON hubcaps!) and specuate forever, but until you pull the head and look at the tops of the pistons, you'll never know if the oil rings are where the consumption issue is or if it's somewhere else. If the oil is coming up from the "bottom side", then there will be "washed" areas on the top(s) of the piston crowns (i.e., clean with no carbon accumulation), typically around the edges. If everything is "dry" (i.e., normal carbon accumuation that is hard and/or somewhat fluffy in charcoal appearance), then the oil is coming in through the "top side" (i.e., intake ports by some means).

As far as manifold vacuum goes, it is a somewhat primitive method of diagnosis, but can indicate internal engine issues if the readings and needle action can be correctly interpreted. ALSO, manifold vacuum typically decreases 1" hg for each 1000 ft of elevation above sea level. And that does not start to also address the issue of just how accurate the vacuum gauge is!

When vacuum gauge diagnosis was popular was when a "dwell tach" was somewhat exotic for the smaller repair shops to have. Nothing wrong with that, per se, just that you have to understand the general orientation of the automotive repair business in the general time frame in which the vehicle was built and lived when new. A good mechanic (back then) could usually tell (from experience with particular vehicle brands/models/engines) what was causing what from visual cues and mileage on the vehicle (before they lost some of their effectiveness). Piston rings generally did not last nearly as long as they did on later and more current vintage engines. Nor was the oil quality to the same level as it was in later years.

With respect to oil use and compression values, I had a similar conversation with a dealership service manager (at a local Chrysler dealership, with the old-line Chrysler service manager that remembered working on Dodge Brothers cars and rode an Indian motorcycle in his younger days). That's where the reality of what you're really measuring with a compression test was revealed--each ring on the piston has a particular and specific purpose for being there (i.e., compression, oil control, oil scraper). Therefore, I have a little feel for the conversation and information you're seeking on this subject.

As for specific vacuum gauge readings, I've tried to use that method to diagnose and tune--finding diagnosis articles from the 1960s in the process. By experience, you can do it a lot quicker and more accurately with a good dwell tach than with a vacuum gauge. If you want to check "running compression", all you have to do is short out (or, if you're brave and quick) pull plug wires out of the distributor cap and look for "rpm drop" each time you do. That's a lot quicker to find a weak cylinder than most any other thing I have observed. Later Sun Scopes had buttons you could push to kill one cylinder at a time, which is much "safer" than the other way (described) and without any possible "additional hand/mouth movements" when some electrons jump where they weren't desired to jump, as they are always searching for "ground". ALWAYS use a quality, rubberized, fender cover when doing this manually (for added electrical insulation).

And, of course, the best way to determine just where the oil MIGHT be coming from is to do a full teardown and inspection. Otherwise, it's just speculation.

Which means the real options are to get ready for a weekend of disassembly and investigation (with appropriate parts/gaskets to put things back together with) or continue using the vehicle as you have been. It might get a little better with additional use, but not "cured".

Just some thoughts and observations . . .

NTX5467

[Clipper47]

Ps- Dave did you take a vac reading when you had your problem?

No I didn't. I pulled a few plugs and they were saturated with oil yet I had not noticed an undue amount of smoke perhaps because I was driving at highway speeds. I recall it was an Edelbrock manifold and I was not very familiar with installing such things. I had put silicone on the ends in place of the proper gasket or perhaps only silicone at the corners. I can say that when I replaced the gaskets I drove the vehicle back the 400 miles and had no problem with it ever after. <span style="font-weight: bold">It was oil getting into the cylinders from a leak at the manifold gasket.</span> The plugs were heavily fouled with oil but I'm not sure if they all were or only a few but that was the clue as to why the vehicle had used so much oil in such a short time.